VAC Live is a Valve anti-cheat mechanism that works not after a match and not on a schedule, but right in the middle of the game. The name stands for Valve Anti-Cheat Live: the familiar VAC system gets a "live" check, that is, one performed at the moment a player is on the server.
How it differs from regular VAC
A classic VAC ban, as a rule, does not arrive right away: the system collects data, and the ban is issued later. A player could finish several matches and only then find out that their account had been banned. For more on the ban itself, see the article on [VAC ban](/vac-ban).
VAC Live works differently: if the protection determines that an account showing signs of violations, or a banned account, is taking part in a match, the game is cut short for it immediately. For the other participants this looks like a sudden end or cancellation of the match: the system steps in where before one had to wait for the results of a check.
How the term is used
Players and viewers use the term in several senses:
- as the name of the whole instant-check system ("VAC Live kicked in");
- as the reason a match suddenly ended without a normal result;
- as a topic for discussing how quickly the anti-cheat reacts to violators.
A typical situation: in a ranked game, one of the participants turns out to be linked to a banned account, the system triggers, and the match is aborted. The other players see a message that the game has ended and return to the menu. Such matches should not punish those who played fairly, so the outcome of the game is usually not counted as an ordinary loss or win.
Why it is needed
The idea behind the system is clear: the less time a violator spends in a match, the less they spoil the game for everyone else. Previously, honest players could spend forty minutes on a match and then learn that one of the participants had been using [cheat software](/cheat-software). Instant reaction reduces the damage.
It is important to understand the limits. VAC Live is not a new type of punishment, but a way to apply the anti-cheat's existing decisions faster. Valve does not disclose the details of how exactly the system makes decisions: this is common practice for anti-cheats, because the more is known about a mechanism, the easier it is to find ways around it.
Origin of the name
The word "Live" in the name indicates real-time operation, and the abbreviation VAC stands for Valve Anti-Cheat. The general principle of how the protection works is described in the article on [anti-cheat](/anti-cheat).